check_nagios_summary enables you to do perform distributed monitoring using Nagios. With this plugin, a Nagios system can check and summarize the status of other (satelite) Nagios systems.
Nagios includes NSCA which enables you to distribute check-results of satelite Nagios processes to the main Nagios instance. The con of this is that it requires you to have all services defined on the satelite host to be defined on the main host as well. This is an administration nightmare.
NagiosDigger: a web-interface to the historical Nagios logging. Nagcon: a console application interfacing to Nagios which gives you an overview of all services with troubled services. NagIRCBot announces the Nagios status on an IRC channel. NagTail is like tail on the Nagios status logfile.